Release: Flatpak bundles, AppImage zsync updates, README Downloads (#500)

* Release: Flatpak x86_64/aarch64 bundles, AppImage zsync updates, README Downloads

- New `flatpak` matrix job (ubuntu-24.04 and ubuntu-24.04-arm) repackages each Linux tarball
  into vectorcraft-<ver>-linux-<arch>.flatpak via packaging/linux/flatpak-bundle.sh and the
  new ai.storyteller.vectorcraft.bundle.yml; packaging-lint keeps its runtime and finish-args
  identical to the from-source Flathub manifest.
- AppImages embed gh-releases-zsync update information and ship a .zsync beside them; the
  Linux job checks both.
- Jobs that sign nothing (version, linux, flatpak, freebsd, web) leave the `release`
  environment, so a branch workflow_dispatch is a dry run; the draft-release job still needs
  the signed macOS/Windows jobs.
- README: a Downloads section listing every build; docs/releasing.md updated.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

* Release: read AppImage update info without extract-and-run

With APPIMAGE_EXTRACT_AND_RUN=1 the runtime forwards --appimage-updateinformation to the app,
which then tries to open a window and fails on the headless runner.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

---------

Co-authored-by: Brandon Thomas <[email protected]>
Co-authored-by: Claude Opus 5.5 <[email protected]>

packaging/linux/flatpak/ai.storyteller.vectorcraft.bundle.yml

@@ -0,0 +1,47 @@
+# Flatpak manifest for the single-file bundle attached to every GitHub release
+# (vectorcraft-<version>-linux-<arch>.flatpak). Build it with packaging/linux/flatpak-bundle.sh.
+#
+# It repackages the release's own Linux tarball (vectorcraft-<version>-linux-<arch>.tar.gz,
+# built on Ubuntu 22.04 by package.sh) instead of compiling Rust inside flatpak-builder: no
+# network and no vendored crate sources during the build, a few seconds instead of 20+ minutes,
+# and byte-for-byte the same binaries as the AppImage/deb/rpm. The script unpacks the tarball
+# into `stage/` next to a copy of this file. The binaries need glibc >= 2.35 and load X11,
+# Wayland, xkbcommon and Vulkan at runtime; the freedesktop runtime has all of them, and the
+# GPU driver comes from its org.freedesktop.Platform.GL extension.
+#
+# ai.storyteller.vectorcraft.yml (same directory) is the from-source manifest for Flathub. Keep
+# runtime, runtime-version, sdk and finish-args identical in both (packaging-lint checks this).
+id: ai.storyteller.vectorcraft
+runtime: org.freedesktop.Platform
+runtime-version: '25.08'
+sdk: org.freedesktop.Sdk
+command: vectorcraft
+finish-args:
+  # X11 shared memory (MIT-SHM). Without it the X11 fallback is slow or fails.
+  - --share=ipc
+  # Display: Wayland first; X11 only when no Wayland compositor is running.
+  - --socket=wayland
+  - --socket=fallback-x11
+  # GPU access for the wgpu renderer (Vulkan, or GL as a fallback).
+  - --device=dri
+  # Open/Save dialogs use the file-chooser portal (rfd), and drag-and-drop uses the document
+  # portal, so broad filesystem access isn't needed. Pictures is granted for opening files by
+  # path from the command line.
+  - --filesystem=xdg-pictures
+  # Deliberately not granted: network (the optional --control server listens on 127.0.0.1 in
+  # the sandbox; `flatpak override --user --share=network ai.storyteller.vectorcraft` exposes it
+  # to host agents) and home/host filesystem access.
+modules:
+  - name: vectorcraft
+    buildsystem: simple
+    build-commands:
+      - install -Dm755 bin/vectorcraft /app/bin/vectorcraft
+      - install -Dm755 bin/vectorcraft-cli /app/bin/vectorcraft-cli
+      - install -Dm644 share/applications/ai.storyteller.vectorcraft.desktop /app/share/applications/ai.storyteller.vectorcraft.desktop
+      - install -Dm644 share/mime/packages/ai.storyteller.vectorcraft.xml /app/share/mime/packages/ai.storyteller.vectorcraft.xml
+      # Already has the release's version and date substituted by package.sh.
+      - install -Dm644 share/metainfo/ai.storyteller.vectorcraft.metainfo.xml /app/share/metainfo/ai.storyteller.vectorcraft.metainfo.xml
+      - mkdir -p /app/share/icons /app/share/doc && cp -R share/icons/hicolor /app/share/icons/ && cp -R share/doc/vectorcraft /app/share/doc/
+    sources:
+      - type: dir
+        path: stage

packaging/linux/flatpak/ai.storyteller.vectorcraft.yml

@@ -8,6 +8,7 @@
 #   flatpak run ai.storyteller.vectorcraft
 #
 # For Flathub, replace the `dir` source with a `git` source pinned to a release tag and commit.
+# Release bundles (.flatpak on GitHub Releases) use ai.storyteller.vectorcraft.bundle.yml instead.
 id: ai.storyteller.vectorcraft
 runtime: org.freedesktop.Platform
 runtime-version: '25.08'
@@ -16,6 +17,7 @@ sdk-extensions:
   - org.freedesktop.Sdk.Extension.rust-stable
 command: vectorcraft
 finish-args:
+  # Keep identical to ai.storyteller.vectorcraft.bundle.yml (the release bundle); comments there.
   - --share=ipc
   - --socket=wayland
   - --socket=fallback-x11